The present invention is in the field of imaging systems. More particularly, the present invention provides an apparatus and method for picking a single printing plate from a stack of printing plates.
In external drum imaging systems, a movable optical carriage is commonly used to displace an image recording source in a slow scan direction while a cylindrical drum, having recording media mounted on an external surface thereof, is rotated with respect to the image recording source. The drum rotation causes the recording media to advance past the image recording source along a fast scan direction that is substantially perpendicular to the slow scan direction.
The image recording source may include an optical system for generating one or more imaging beams that are scanned across the surface of the recording media. Each imaging beam may be separately modulated according to a digital information signal representing data corresponding to the image to be recorded.
The recording media to be imaged by an external drum imaging system is commonly supplied in discrete, flexible sheets, hereinafter collectively referred to as xe2x80x9cprinting plates.xe2x80x9d Each printing plate may comprise one or more layers supported by a support substrate, which for many printing plates is a plano-graphic aluminum sheet. Other layers may include one or more image recording (i.e., xe2x80x9cimageablexe2x80x9d) layers such as a photosensitive, radiation sensitive, or thermally sensitive layer, or other chemically or physically alterable layers. Printing plates that are supported by a polyester support substrate are also known and can be used in the present invention. Printing plates are available in a wide variety of sizes, typically ranging, e.g., from 9xe2x80x3xc3x9712xe2x80x3, or smaller, to 58xe2x80x3xc3x9780xe2x80x3, or larger.
A cassette is often used to supply a plurality of unexposed printing plates to an external drum imaging system. The printing plates are normally supplied in stacks of ten to one hundred, depending upon plate thickness and other factors, and are stored in the cassette. Interleaf sheets, commonly referred to as xe2x80x9cslip sheets,xe2x80x9d may be positioned between the printing plates to protect the emulsion side of the printing plates from physical damage (e.g., scratches), which could render a printing plate unusable for subsequent printing. When Interleaf sheets are not used, great care must be taken to avoid emulsion damage as each printing plate is separated from the stack, fed from the cassette into the external drum imaging system, and mounted on the external drum. Unfortunately, preventing such damage as the printing plates are unloaded and fed from a cassette to an external drum has proven to be a very difficult and expensive task in currently available external drum imaging systems, especially when larger (e.g., 45xe2x80x3 wide) printing plates are used.
The present invention provides an apparatus and method for picking a single printing plate from a stack of printing plates in an imaging system.
Generally, the present invention provides an apparatus, comprising:
a plurality of suction cups, a peeler, and a system for rotatably displacing the suction cups relative to the peeler, wherein a center line of rotation of the displacing system is located on a surface of the peeler.
The present invention also provides an apparatus for picking a printing plate from a stack of printing plates, comprising:
a plurality of suction cups, a peeler, a drive system for displacing the suction cups and the peeler against a surface of a top printing plate on the stack, a vacuum source for supplying a vacuum to the suction cups to secure the suction cups against the surface of the top printing plate, and a system for rotatably displacing the suction cups relative to the peeler to peel a portion of the top printing plate off of the stack, wherein a center line of rotation of the displacing system is located at a contact point between the peeler and the surface of the top printing plate.
The present invention further provides a method for picking a printing plate from a stack of printing plates, comprising:
displacing a plurality of suction cups and a peeler against a surface of a top printing plate on the stack;
supplying a vacuum to the suction cups to secure the suction cups against the surface of the top printing plate; and
rotatably displacing the suction cups relative to the peeler to peel a portion of the top printing plate off of the stack, wherein a center line of rotation of the displacement is located at a contact point between the peeler and the surface of the top printing plate.
The present invention also provides a method for picking a printing plate from a stack of printing plates, comprising:
displacing a plurality of suction cups and a peeler against a surface of a top printing plate on the stack;
supplying a vacuum to the suction cups to secure the suction cups against the surface of the top printing plate; and
peeling a portion of the top printing plate off of the stack, and preventing relative motion of the top printing plate against an underlying printing plate on the stack, by rotatably displacing the suction cups relative to the peeler, wherein a center line of rotation of the displacement is located at a contact point between the peeler and the surface of the top printing plate.